Granulates containing feed-enzymes

ABSTRACT

The present invention describes a process for the preparation of an enzyme-containing granulate wherein an aqueous enzyme-containing liquid is, optionally supplemented with a solid carrier and/or additive ingredients, processed into granules, dried and subsequently coated with a polyolefin, preferably polypropylene and/or polyethylene. This coated enzyme granulate is suitable for the manufacture of animal feed compositions by mixing the granulate with feed ingredients, treating with steam and pelleting. The coated granulates show high enzyme stability during pelleting conditions and during storage. At the same time, the dissolution time of the granule is very short so that the bioavailability of the enzyme to the animal is improved.

RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. 371)of PCT/EP03/00342 filed Jan. 14, 2003, which claims the benefit ofEuropean application 02075016.2 filed Jan. 15, 2002.

FIELD OF THE INVENTION

The present invention relates to the formulation of enzymes, preferablyfeed-enzymes, into granulates. These (edible) granulates can then beused in animal feed.

BACKGROUND OF THE INVENTION

Animal feed represents one of the largest costs incurred in keepinglivestock and other animals. The use of various enzymes in animal, e.g.livestock, feed has become almost common practice. These enzymes areusually produced by culturing micro-organisms in large scale fermentersoperated by industrial enzyme producers. At the end of the fermentation,the resulting “broth” is usually subjected to a series of filtrationsteps to separate the biomass (the micro-organisms) from the desiredenzyme (in solution). Subsequently the enzyme solution is concentratedand processed as a liquid (often after addition of various stabilisers)or to a dry formulation.

For economical and practical reasons, dry enzyme formulations are oftenpreferred to liquid enzymes formulations. Nevertheless, even when a dryenzyme formulation is chosen, some steps of the feed pelleting process,such as conditioning, may be detrimental to the enzyme. Various enzymemanufacturers have developed alternative formulation methods to improvethe stability of dry enzyme products during pelleting and storage of thefeed. For instance, an option is to coat the enzyme-containing granulewith a suitable coating agent.

EP 0 569 468 refers to a formulation consisting of an enzyme-containinggranulate that is coated with a high melting wax or fat alleged toimprove resistance to pelleting conditions. A disadvantage of such acoating is that the dissolution time of the granulate is long (about onehour). Therefore the bio availability of the enzyme to the animal isdecreased. In addition, the granulates have a wide particle sizedistribution which makes it difficult to obtain an evenly distributedenzyme concentration after coating, since small particles contain arelatively high amount of coating agent as compared to large particles.

WO 00/47060 discloses the use of polyethylene glycol (PEG) as a coatingmaterial. These PEG coatings have the disadvantage that they do notincrease the pelleting stability of the enzyme granulate to the desiredlevel.

There is thus still a need for stable formulations of enzymes for use inanimal feed that are cheap and easy to produce and that combine asatisfactory pelleting stability with good bio availability of theenzyme to the animal.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a process for the preparation of anenzyme-containing granulate suitable for use in an animal feed, theprocess comprising obtaining a dry enzyme-containing granule and coatingthe granules with a polyolefin. The coating of an enzyme granulate withsuch a polymer provides for a low water uptake during the conditioningstep of the feed preparation process and, surprisingly, an attractivelyshort dissolution time of the enzyme granule. Thus, the use of apolyolefin coating according to the present invention provides theadvantage of a fat-type coating (pelleting stability) combined with theadvantage of a hydrophilic coating (short dissolution time).

The polyolefin used in the process of the invention is an olefin polymerwherein the olefin (hydrocarbon) monomers have a length of 2 to 10carbon atoms. Preferably, the olefin monomers have a length of 2 to 4carbon atoms, wherein it is envisaged to optionally include monomerswith a chain length of 5 to 10 carbon atoms in the polymerisationprocess, to obtain a polymer with short-chain branches. Preferably, thepolyolefin which is used according to the invention is selected from thegroup consisting of polyethylene, polypropylene, polybutylene and/orpolybutadiene (according to new nomenclature these polymers are calledpolyethene, polypropene, polybutene, polybutadiene). More preferably,the polyolefin is polyethylene and/or polypropylene.

The polyolefin used in the process of the invention preferably has amelting point which is sufficiently high to prevent melting of thepolyolefin coating under feed pellet preparation conditions. Morepreferably, the polyolefin has a melting range ending at a temperatureranging from 100 to 200° C. (border values included), even morepreferably from 105 to 190° C., most preferably from 120 to 180° C.

The polyolefin is a substantially linear polymer, i.e. a polymer whichis not branched or only displays a low degree of branching. Asubstantially linear polymer thus may include a linear polymer withshort side chains, i.e. side chains with a length of at the most around10 carbon atoms.

For polyethylene, the molecular weight may be in the range of3000-20,000 Da.

In a preferred embodiment of the invention, the polyolefin is applied tothe granules in the form of a dispersion of polyolefin particles in asuitable solvent.

To enable the formation of a suitable layer on the granule to be coated,the dispersion preferably has a particle size as specified below and/oris homogeneous and/or is physically stable. More preferably, thepolyolefin particles in the dispersion have a size ranging from 10 to1000 nm (border values included), even more preferably from 10 to 500nm, most preferably from 10 to 200 nm.

The polyolefin dispersion is advantageously capable of forming ahomogeneous layer upon drying of the coated granules.

The polyolefin dispersion further is advantageously capable of forming awater-insoluble layer upon drying at a relatively low temperature,typically a temperature substantially below the melting point of thepolyolefin.

The polyolefin dispersion further is advantageously capable of forming athin layer that does not form cracks upon drying. The thin layertypically has a thickness of 50 μm or less, preferably of 20 μm or less,more preferably 10 μm or less. A lower limit in the thickness of thelayer may be 1-2 μm. The thickness of the layer may be influenced by thepolyolefin content of the dispersion.

A suitable solvent to disperse the polyolefin particles is a solventwherein the polyolefin is insoluble, e.g. a hydrophilic solvent likewater or ethanol. Preferably, water is used as a solvent. The dispersiontypically may contain 10 to 60% polyolefin in solvent (w/w), preferably20 to 40% polyolefin in solvent.

In a preferred embodiment of the invention, the polyolefin dispersion isa dispersion of polyolefins containing acidic groups which arestabilized with an amine, preferably a volatile amine. The acidic groupspreferably are carboxylic groups and the volatile amine preferably isammonia.

Carboxylic groups may conveniently be introduced into the polyolefin by,for instance, oxidation. The amount of acidic groups introduced in thepolyolefin is characterised by the so-called acid number. The acidnumber of the polyolefin may range between 2 and 30 (border valuesincluded), preferably between 4 and 30, more preferably between 12 and18, in the case of polyethylene.

Additional compounds may be added to the polyolefin dispersion to conferfavourable characteristics to the dispersion. For instance, thepolyolefin particles may be physically stabilised with specificcompounds to prevent clotting and/or to prevent sedimentation. Thedispersion may also contain compounds which promote the formation of awater-insoluble film upon drying.

Examples of additional compounds are surfactants or amines.

The polyolefin coating preferably is applied at 0.1-20% (weightpolyolefin per weight of the granules), more preferably at 0.2-10% andmost preferably at 0.4-5%. The percentages used throughout thisspecification refer to dry weight percentages and, unless indicatedotherwise, are based on the weight of the dry granulate, before coating.

To apply the polyolefin and, optionally, other coating material(s) ontothe granulate a number of known methods are available which include theuse of a fluidised bed, a high shear granulator, a mixer granulator, ora Nauta-type of mixer. In a preferred method for application of thepolyolefin onto the granulate, the polyolefin is sprayed as a dispersiononto a fluidized bed of the granules to be coated.

The granule to be coated according to the present invention comprises afeed enzyme, optionally, a solid carrier and, optionally, one or moreadditives.

The granule typically may comprise particles, 90% having a size of 300μm or larger, with an upper size limit of about 3 mm. Alternatively, thegranulate may be a microgranulate, 90% of its particles having a size of300 μm or less, with a lower size limit of 10-25 mm.

The solid carrier that may be used in the preparation of the granulatefor instance is a powder which can be compacted into a granule and whichpreferably has an average particle size ranging between 5 and 20 μm.

For instance, the solid carrier may essentially consist of an ediblecarbohydrate polymer. The numerous advantages of the use of an ediblecarbohydrate polymer are presented in patent application WO 98/54980.

An edible carbohydrate polymer is a carbohydrate polymer which isallowed for use as a feed additive. The edible carbohydrate polymer ischosen so that it is edible by the animal for whom the feed is intended,and preferably digestible as well. The polymer preferably compriseshexose polymer units, more preferably glucose polymer units. Mostpreferably the carbohydrate polymer comprises α-D-glucopyranose units,amylose (a linear (1→4) α-D-glucan polymer) and/or amylopectin (abranched D-glucan with α-D-(1→4) and α-D-(1→6) linkages). Starch is thepreferred carbohydrate polymer. Other suitable hexose-containingpolymers that can be used instead of, or in addition to starch, includeα-glucans, β-glucans, pectin (such as proto-pectin), and glycogen.Derivatives of these carbohydrate polymers, such as ethers and/or estersthereof, are also contemplated. Suitably the carbohydrate polymer iswater-insoluble.

In other embodiments of the invention, one or more additionalingredients may be incorporated into the granulate, e.g. as processingaids and/or for further improvement of the pelleting stability and/orthe storage stability of the granulate. A number of such additives arediscussed below.

In one embodiment of the invention, the additive comprises a watersoluble inorganic salt (as suggested in EP 0 758 018). Preferably, thegranules comprise at least 0.1% of a water soluble inorganic saltcomprising a divalent cation, more preferably zinc. Most preferably, theinorganic salt is zinc-sulphate. The end product preferably containsfrom 500-1,500 mg Zn/kg end product, more preferably 700-1,300 mg Zn/kgend product and most preferably 900-1,100 mg Zn/kg end product. Divalentcations are preferred because they provide the best storage andprocessing stability. Sulphate is preferred as anion because it providesthe best drying yield. The salts may be added (e.g. to the mixture) insolid form. Alternatively, the salt(s) may be dissolved in the water orenzyme-containing liquid, for instance prior to mixing with the solidcarrier.

Further improvement of the pelleting stability may be obtained by theincorporation of hydrophobic, gel-forming and/or slowly dissolvingcompounds into the formulation. These may be provided by adding at least0.1% (w/w), preferably at least 0.5% and more preferably at least 1% ofthe desired compound (based on the weight of water and, if present,solid carrier ingredients) to the mixture to be processed to granules.Suitable substances include derivatised celluloses, such as HPMC(hydroxy-propyl-methyl-cellulose), CMC (carboxy-methyl-cellulose), HEC(hydroxy-ethyl-cellulose), polyvinyl alcohols (PVA); and/or edible oils.Edible oils, such as soy oil or canola oil, may be added (e.g. to themixture to be granulated) as a processing aid.

In the process of preparing a granulate, the enzyme and water arepreferably provided as an enzyme-containing (preferably aqueous) liquid,such as a solution or a slurry, that is from, or derived from, amicrobial fermentation process. This fermentation process will usuallybe one in which the enzyme is produced. The fermentation process mayresult in a broth which contains the micro-organisms (which produced thedesired enzyme) and an aqueous solution. This aqueous solution, onceseparated from the micro-organisms (for example, by filtration) can bethe enzyme-containing aqueous liquid used in the invention. Thus inpreferred embodiments the enzyme-containing aqueous liquid is afiltrate. Usually the enzyme will be in an active form. Preferably theliquid is in a concentrated form, such as an ultra-filtrate (UF), whichmay allow the production of a granulate with a desired activity level.

If a solid carrier is used, the amount of enzyme-containing liquid (andso enzyme) that can be absorbed onto the carrier is usually limited bythe amount of water that can be absorbed. The enzyme solution maycontain about 25% (w/w) dry matter. The amount of water added to thesolid carrier is such that (substantially) all the water in the aqueousliquid is absorbed by all the components present in the solid carrier.The use of higher temperatures in order to absorb a greater amountenzyme-containing liquid is also contemplated by the present invention,and indeed is preferable especially when dealing with thermostableenzymes. For these enzymes therefore mixing of the solid carrier andliquid (or enzyme and water) is performed at a temperature above 30° C.,preferably above 40° C. and more preferably above 50° C. Alternativelyor in addition, the liquid may be provided at this temperature. Ingeneral, non-swelling conditions of the solid carrier (at lowertemperatures) are preferred to minimise loss arising from instability of(heat sensitive) enzymes at higher temperatures.

The water or enzyme-containing liquid may comprise one or moreenzyme(s). Suitable enzyme(s) are feed enzymes to be included in animalfeed (including pet food). The function of these feed enzymes is oftento improve the feed conversion rate, e.g. by reducing the viscosity orby reducing the anti-nutritional effect of certain feed compounds. Feedenzymes (such as phytase) may also be used such as to reduce the amountof compounds in the manure which are harmful to the environment.

In one embodiment, granules are prepared that contain a highconcentration of an enzyme. The advantages of preparing phytasecompositions at a high concentration were already described in WO98/55599.

Suitable enzymes include: phosphatases, such as phytases (both3-phytases and 6-phytases) and/or acid phosphatases, carbohydrases, suchas amylolytic enzymes and/or plant cell wall degrading enzymes includingcellulases such as β-glucanases and/or hemicellulases such as xylanasesor galactanases and/or pectinases, proteases or peptidases such aslysozyme, galactosidases, esterases, lipases, phospholipases such as themammalian pancreatic phospholipases A2 and glucose oxidase. Preferably,the feed enzyme at least is an enzyme selected from the group consistingof phytases, xylanases, β-glucanases, proteases, phospholipases andglucose oxidases. More preferably, the feed enzyme at least is an enzymeselected from the group consisting of phytases and xylanases.

If the enzyme is a phytase, then the final granulate may preferably havean enzyme activity ranging from 4,000 to 20,000 FTU/g, more preferablyfrom 5,000 to 20,000 FTU/g, most preferably from 5,000 to 15,000 FTU/g.One Phytase Unit (FTU) is thereby defined as the amount of enzyme whichliberates 1 μmol inorganic phosphate per minute from sodium phytate(0.0051 mol/liter) at 37° C. and at a pH of 5.5 under the conditionsthat phytase activity was determined according to the procedure“ISL-method 61696” (manual molybdate-vanadate assay).

If the enzyme is a xylanase, then the final granulate may preferablyhave an enzyme activity ranging from 5,000 to 100,000 EXU/g, morepreferably from 10,000 to 100,000 EXU/g, and most preferably from 15,000to 100,000 EXU/g. One Endo-Xylanase Unit (EXU) is thereby defined as theamount of enzyme which liberates 4.53 μmol reducing sugars, measured asxylose equivalents, per minute under the conditions of the procedure“ISL-method 61731”.

ISL-methods are obtainable on request from DSM, Food Specialties, AgriIngredients, A. Fleminglaan 1, P.O. Box 1, 2600 MA, Delft, TheNetherlands.

In addition to these feed enzymes, the invention is equally applicableto non-enzymatic polypeptides with biological activities, such asantigenic determinants to be used as vaccines and/or polypeptidesengineered to have an increased content of essential amino acids, ofwhich the biological activity may be sensitive to thermal inactivation.

The granulate to be coated according to the invention may be prepared bydrying an enzyme-containing aqueous solution, for instance anultra-filtrate as described hereinbefore, in particular by spray dryingor multistage drying. Optionally, additives may be added prior to orduring drying, for instance as processing aids or to improve pelletingstability. Furthermore, an inert compound or material may be addedduring drying, for instance an inorganic salt, maltodextrins, granulatedflour, resulting in so called co-drying.

Alternatively, the granulate to be coated may be prepared bymechanically processing a mixture of the enzyme, water (e.g. anenzyme-containing liquid), a solid carrier and optionally additives byknown techniques frequently used in food, feed and enzyme formulationprocesses. This mechanical processing for instance comprises expansion,extrusion, spheronisation, pelleting, high-shear granulation, drumgranulation, fluid bed agglomeration or a combination thereof. Theseprocesses are usually characterised by an input of mechanical energy,such as the rotation of a screw or a mixing mechanism, the pressure of arolling mechanism of a pelleting apparatus, the movement of particles bya rotating bottom plate of a fluid bed agglomerator or the movement ofthe particles by a gas stream, or a combination thereof. These processesallow the solid carrier (e.g. in the form of a powder), to be mixed withthe enzyme and water, for example an enzyme-containing liquid (anaqueous solution or slurry), and so subsequently granulated.Alternatively the solid carrier can be mixed with the enzyme (e.g. in apowder form) to which water, such as a liquid (or slurry) is then added(which can act as granulating liquid).

In yet a further embodiment of the invention, the granulate (e.g. anagglomerate) is formed by spraying or coating the enzyme-containingliquid onto a carrier, such as in a fluid bed agglomerator. Here theresulting granules can include an agglomerate as can be produced in afluid bed agglomerator. Preferably the mixing of the enzyme-containingliquid and the solid carrier additionally comprises kneading of themixture before extrusion. This may improve the plasticity of the mixturein order to facilitate granulation.

If the granulate is formed by extrusion this is preferably performed atlow pressure. This may offer the advantage that the temperature of themixture being extruded will not, or only slightly, increase.Low-pressure extrusion includes extrusion for example in a FujiPaudal-type of basket- or dome-extruder.

The extrudate obtained can be subjected to rounding off (e.g.spheronisation), such as in a Marumeriser™ and/or compaction. Theextrudate can be spheronised prior to drying since this may reduce dustformation in the final granulate and/or may facilitate any coating ofthe granulate.

The granules can then be dried, such as in a fluid bed drier or, in caseof the fluid bed agglomeration, can be immediately dried (in theagglomerator) to obtain (solid dry) granulates. Other known methods fordrying granules in the food, feed or enzyme industry can be used by theskilled person. Suitably the granulate is flowable. The dryingpreferably takes place at a product temperature from 25 to 60° C.,preferably from 30 to 50° C.

The dry granulate thus obtained then is subjected to the coating with apolyolefin according to the invention. The present invention furtherenvisages that a granulate may be coated with a coating layer differentform a polyolefin coating layer, prior to applying the polyolefin layer.

Preferably the granules obtained after coating have a relatively narrowsize distribution (e.g. they are monodisperse). This can facilitate ahomogeneous distribution of the enzyme granulate in the feed pellets.The process of the invention tends to produce granulates with a narrowsize distribution. The granules may be of irregular (but preferablyregular) shape, for example approximately spherical.

If necessary, an additional step may be included in the process tofurther narrow the size distribution of the granules, such as screening.

The enzyme-containing granulate obtainable by the process according tothe invention (which forms another aspect of the invention) seeks tosolve or at least mitigate the problems encountered in the prior art.These coated granulates have a high pelleting stability and a shortdissolution time. Therefore the bioavailability of the enzyme to theanimal is improved as compared to classical fat-coated granules.

The invention thus provides an enzyme-containing granulate obtainable bythe above-mentioned processes and having the following characteristics.The granulate consists of granules containing a feed enzyme, optionally,a solid carrier and, optionally, one or more additives, coated with apolyolefin layer.

The granulate of the invention is suitable for use in the preparation ofan animal feed. In such processes the granulate is mixed with feedsubstances, as such, as part of a premix or as precursor to an animalfeed. The characteristics of the granulate according to the inventionallows its use as a component of a mixture which is well suited as ananimal feed, especially if the mixture is steam treated, subsequentlypelleted and optionally dried.

Thus, a further aspect of the present invention relates to a process forthe preparation of animal feed, or a premix or precursor to an animalfeed, the process comprising mixing the granulate provided by thepresent invention with one or more animal feed substances oringredients.

The present invention also relates to a process for promoting the growthof an animal, the process comprising feeding an animal a diet thatcomprises the granulate provided by the invention. Here, the animal dietcan include either the granulate itself, or the granulate present in afeed. Suitable animals include farm animals, such as livestock, pigs andpoultry, and fish.

Another aspect of the invention thus relates to a composition comprisingthe granulate of the invention, which composition is preferably anedible feed composition such as an animal feed.

Still another aspect of the present invention relates to the use of thegranulate of the invention in, or as a component of, an animal feed orfor use in an animal diet.

Preferred features and characteristics of one aspect of the inventionare equally applicable to another mutatis mutandis.

The following Examples are presented merely to illustrate the invention,and are not intended, or to be construed as, being limiting.

EXAMPLES General Methods

Preparation of Phytase-Containing Granules

Phytase-containing granules are prepared according to the processdescribed in WO98/54980.

Conditioning/Pelleting Step:

50 grams granules were mixed in 10 kg feed of the premix of choice andmixed just before the test with 240 kg of the same recipe. This 250 kgmixture was dosed in a mixer/conditioner by a dosing screw, at a speedof 600 kg/h, where it was heated by direct steam around 80° C. Theresidence time was about 30-40 seconds whereupon the hot mixture waspushed into the pelleting press. The pellets coming out of the die havea temperature between 80 and 82° C. and fall on a cooling belt. Fromthis belt, samples were taken for the stability measurement.

Poultry Feed Used for Analysis of Pelleting Stability:

Maize (50%), peas (5%), soybean meal (28%), tapioca (1.98%), fish meal(2.5%), feather meal (1.5%), soybean oil (1.75%), animal fat (3.5%),Mervit (Premervo, Utrecht, The Netherlands) 100 (1%), limestone (1.1%),mono calcium phosphate (1.22%), salt (0.3%), Mervit 394 (0.65%), Mervit393 (1.5%), up to a total of 100%.

Analysis of Phytase Activity in Feed Pellets:

Phytase activity was determined according to the procedure “ISL-method61696” (manual molybdate-vanadate assay).

Example 1

300 grams uncoated granules (batch NPHG 498) were put into a STREA fluidbed apparatus from NIRO-AEROMATIC.

With a topspray device (two-phase nozzle), various coatings were sprayedonto the granules as indicated in Table 1. These coated granules weretested in the pelleting test as described under General methods.

HS granules are granules coated with a fat+anti-caking coating (>30%)(obtained from Novo Nordisk, batch no. HF 98011450).

TABLE 1 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/81° C. Dissolution Residual time activitySample no. with coating (min.) (%) A uncoated batch 498 1 27 B 10% PEG6000 solution 2 30 C 10% Carnauba wax dispersion 1 36 D 10% PEdispersion Stamylan ® LD1965 1 32 E 10% PE dispersion EXACT ® 8210 20 48F 8% PE Dispersion 1205 5 57 G HS granule >60 55

Surprisingly, the dissolution time of the granulates does not seem tocorrelate with their pelleting stability. The most important parameterto optimise is the dissolution time, since it determines thebioavailability of the enzyme to the animal.

The coatings of samples C and F were bought from Paramelt B.V.(Heerhugowaard, The Netherlands) and of samples D and E from DSMResearch (DSM N.V., Geleen, The Netherlands).

Example 2

The effect of the coating Dispersion 1205 on the pelleting stability ofphytase-containing granulates was tested in large scale production.

In a GPCG 300 fluid bed machine from Glatt, 300 kg of uncoatedgranulate, prepared as described under General methods, was coated with120 kg Dispersion 1205 à19.5% dry matter (sample L) and another batchwith 60 kg PEG 6000 solution à50% dry matter (sample K).

These coated granulates were tested in a pelleting test together withthe uncoated product (sample H) and HS granule of a competitor (sampleM) as described under General methods.

The results are presented in Table 2.

TABLE 2 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/80° C. Dissolution time Residual activitySample no. with coating (min.) (%) H Uncoated batch S4893 1 33 K Coatedwith PEG 6000 2 36 L Coated with PE Dispersion 1205 10 74 MHS-granule >60 76

Example 3

In a Glatt GPCG 1.1 fluid bed coater, 1 kg of uncoated granulate,prepared as described under General methods, was coated with differentcoatings as mentioned in Table 3. Samples O was coated with a melt at atemperature of 80° C. Sample P was coated with a self-made dispersion ofsodium caseinate and hydrogenated coconut fat.

TABLE 3 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/80° C. Dissolution time Residual activitySample no. with coating (min.) (%) N Uncoated batch 5193 1 20 O Coatedwith 10% Waretta fat 4 22 P Coated with 10% fat dispersion 10 25 M HSgranule >60 53

The various fat-type coatings tested (except the one from the HS granuleM) confer a short dissolution time to the granules, but the pelletingstability of the coated granules is not significantly improved ascompared to the uncoated granulate (sample N).

Example 4

The influence of different concentrations of Dispersion 1205 (2 to 24%,samples S to V) on the pelleting stability and on the dissolution timeof the granulate was tested. Uncoated granulates were prepared asdescribed under General methods. The granules were coated as indicatedin Table 4 and tested in a pelleting test as described under GeneralMethods.

The results are presented in Table 4.

TABLE 4 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/80° C. Dissolution time Residual activitySample no. with coating (min.) (%) R Uncoated batch 5193 1 22 S Coatedwith 2% Dispersion 1205 2 31 T Coated with 4% Dispersion 1205 2 49 UCoated with 8% Dispersion 1205 2 58 V Coated with 24% 60 75 Dispersion1205 M HS granule >60 64

The concentration of the polyethylene which is applied to coat thegranules seems to be positively correlated with the dissolution time ofthe granules.

Example 5

In this example the influence of a polypropylene (PP) dispersion and ofpolyethylene (PE) dispersions from different suppliers were tested.Uncoated granules were prepared as described General methods. Thegranules were then coated as indicated in Table 5 and tested in apelleting test as described under general methods.

The results are presented in Table 5.

TABLE 5 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/80° C. Dissolution time Residual activitySample no. with coating (min.) (%) W Uncoated batch 5193 1 21 X Coatedwith 4% Permanol Z (PE) 1 38 Y Coated with 4% Permanol 601 (PP) 1 43 ZCoated with Dispersion 1205 (PE) 1 39

All three coatings, the Permanol samples (X+Y) from Clariant GmbH,Frankfurt am Main) and the Dispersion 1205 from Paramelt BV gave about atwice as high residual activity than the uncoated sample and stillensured the same dissolution time.

The Permanol 601 is a PP coating with a higher melting point (30° C.higher) than the PE, but also with a larger particle size (10 timeslarger) in the dispersion than the Dispersion 1205.

Example 6

In this example another comparison of the influence of a polypropylene(PP) dispersion and of polyethylene (PE) dispersions from differentsuppliers was made. Uncoated granules were prepared as described inGeneral methods. The granules were then coated as indicated in Table 6and tested in a pelleting test as described under General methods.

The results are presented in Table 6.

TABLE 6 Residual phytase activity in poultry feed in % afterconditioning/pelleting at 80/80° C. Dissolution Residual time activitySample no. with coating (min.) (%) A uncoated batch R2236/R3305 1 31 BCoated with 4% PE Dispersion 1286 1 42 C Coated with 4% Permanol Z (PE)1 44 D Coated with 4% Permanol AAP5 (PP) 1 41 E Coated with 4% PermanolAAP5 with 1 46 ammonia (PP) F Coated with 4% Polygen WE6 (BASF) 1 40 GCoated with 4% Polygen WE7 (BASF) 1 39

All three coatings, the Permanol (C, D, E) samples from Clariant GmbH,Frankfurt am Main, the Dispersion 1286 from Paramelt BV (B) and thePolygen WE6 and WE7 coatings (F, G) from BASF Aktiengesellschaft,Ludwigshafen, gave significant higher residual activity than theuncoated sample and still ensured the same dissolution time.

1. A process for the preparation of a coated enzyme-containing granulatecomprising forming a dry enzyme containing granulate and coating thegranulate with a polyolefin wherein the coated enzyme-containinggranulate is suitable for use in an animal feed, and wherein thepolyolefin is polyethylene, polypropylene, polybutylene, and/orpolybutadiene.
 2. The process according to claim 1 wherein thepolyolefin is applied at 0.1-20% weight polyolefin per weight of thegranulate.
 3. The process according to claim 1, wherein the upper limitof the melting range of the polyolefin is from a temperature of 100° C.to and including 200° C.
 4. The process according to claim 1, whereinthe polyolefin is applied to the granulate as a dispersion of polyolefinparticles in a suitable solvent.
 5. The process according to claim 4,wherein the solvent is water.
 6. The process according to claim 4,wherein the polyolefin particles have a size ranging from 10 to andincluding 1000 nm.
 7. The process according to claim 4, wherein thepolyolefin dispersion contains 10 to 60% (w/w) polyolefin.
 8. Theprocess according to claim 1, wherein the enzyme is a phytase, xylanase,β-glucanase, protease, phospholipase, amylase and/or glucose oxidase. 9.An enzyme-containing granulate coated with a polyolefin prepared by theprocess according to claim
 1. 10. A process for the preparation of ananimal feed, or a premix or precursor to an animal feed, the processcomprising mixing the granulate of claim 9 with one or more animal feedsubstances or ingredients.
 11. The process according to claim 10,wherein the mixture of feed substance(s) and granulate is treated withsteam, pelletised and cooled.
 12. A feed composition comprising thegranulate according to claim
 9. 13. A process for promoting the growthof an animal, the process comprising feeding an animal a diet thatcomprises the granulate according to claim
 9. 14. A method of producingan animal feed or a component in an animal diet comprising combining thegranulate of claim 9 with animal feed or providing the granulate as acomponent in an animal diet.
 15. The process according to claim 1wherein the polyolefin is applied at 0.2-10% weight polyolefin perweight of the granulate.
 16. The process according to claim 1 whereinthe polyolefin is applied at 0.4-5% weight polyolefin per weight of thegranulate.
 17. The process according to claim 1, wherein the upper limitof the melting range of the polyolefin is from a temperature of 120 toand including 180° C.
 18. The process according to claim 4, wherein thepolyolefin particles have a size ranging from 10 to and including 500nm.
 19. The process according to claim 4, wherein the polyolefinparticles have a size ranging from 10 to and including 200 nm.
 20. Theprocess according to claim 4, wherein the polyolefin dispersion contains20 to 40% (w/w) polyolefin.
 21. A process for promoting the growth of ananimal, the process comprising feeding an animal a diet that comprisesthe composition according to claim 12.